Diagrid structural systems are emerging as structurally efficient as well as architecturally significant assemblies for tall buildings. . The evolution of tall building structural systems based on new structural concepts with newly adopted high strength materials and construction methods have been towards “stiffness” and “lightness”. Structural systems are become “lighter” and “stiffer”. It is common knowledge that rather than directly standing the forces, it is better to reduce them and dissipate the magnitude of vibrations. Structure design of high rise buildings is governed by lateral loads due to wind or earthquake. Lateral load resistance of structure is provided by interior structural system or exterior structural system. The selected structural system should be such that it should be effectively utilized for structural requirements. Recently diagrid structural system is adopted in tall buildings due to its structural efficiency and flexibility in architectural planning.

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Dr. Yousse Hammida

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‫الشبكية‬ ‫الخاليا‬ ‫جمل‬ ‫انواع‬Diagrid Structural System
-‫المع‬ ‫شبكيات‬ ‫الى‬ ‫باالضافة‬‫والجاهزة‬ ‫الستيل‬ ‫ومقاطع‬ ‫دنية‬‫والبواري‬ ‫االنبوبية‬ ‫البروفيالت‬ ‫من‬
‫الشبكات‬ ‫يوجد‬ ‫كذلك‬‫الصنع‬ ‫مسبقة‬ ‫الى‬ ‫المسلحة‬ ‫الخرسانية‬ ‫والمقاطع‬
-‫الخشبية‬ ‫الشبكيات‬ ‫جملة‬ ‫وكذلك‬
-‫واال‬ ‫األبنية‬ ‫تناسب‬ ‫المعدنية‬ ‫والمقاطع‬ ‫الجمل‬ ‫تبقى‬ ‫لكن‬‫العالية‬ ‫رتفاعات‬‫حتى‬011‫طابق‬
-‫المسلحة‬ ‫البيتنونية‬ ‫والمقاطع‬ ‫الشبكات‬ ‫عكس‬ ‫على‬‫من‬ ‫اكثر‬ ‫ليس‬01‫طابق‬
‫الثقيلة‬ ‫والمقاطع‬ ‫الخرسانية‬ ‫الشدة‬ ‫كلفة‬ ‫زيادة‬ ‫الى‬

6. 6

7. 7
SUMMARY
Diagrid has good appearance and it is easily recognized. The configuration and
efficiency of a diagrid system reduce the number of structural element required on
the façade of the buildings, therefore less obstruction to the outside view.
The structural efficiency of diagrid system also helps in avoiding interior and corner
columns, therefore allowing significant flexibility with the floor plan. Perimeter
“diagrid” system saves approximately 20 percent of the structural steel weight
when compared to a conventional moment-frame structure
The diagonal members in diagrid structural systems can carry gravity loads as well
as lateral forces due to their triangulated configuration. Diagrid structures are more
effective in minimizing shear deformation because they carry lateral shear by axial
action of diagonal members. Diagrid structures generally do not need high shear rigidity
cores because lateral shear can be carried by the diagonal members located on the
periphery

8. 8
Diagrid structural systems
are emerging as structurally efficient as well as architecturally significant
assemblies for tall buildings.
. The evolution of tall building structural systems based on new structural
concepts with newly adopted high strength materials and construction methods
have been towards “stiffness” and “lightness”. Structural systems are become
“lighter” and “stiffer”.
It is common knowledge that rather than directly standing the forces,
it is better to reduce them and dissipate the magnitude of vibrations.
Structure design of high rise buildings is governed by lateral loads due to
wind or earthquake.
Lateral load resistance of structure is provided by interior structural system
or exterior structural system.
The selected structural system should be such that it should be effectively
utilized for structural requirements.
Recently diagrid structural system is adopted in tall buildings due to its
structural efficiency and flexibility in architectural planning.

9. 9
‫نظ‬‫ا‬‫م‬‫الجمل‬‫الهيكلية‬‫الشبكية‬Diagrid
‫آخذ‬‫الظهور‬ ‫في‬‫و‬‫ا‬‫ل‬‫ت‬‫ط‬‫و‬‫ر‬‫ودعم‬‫الهيكلية‬ ‫الكفاءة‬‫تأثير‬ ‫هو‬ ‫كما‬‫ا‬‫ل‬‫عوامل‬‫ا‬‫ل‬‫م‬‫ع‬‫م‬‫ا‬‫ر‬‫ي‬‫ة‬‫ذات‬
‫األهمية‬‫الشاهقة‬ ‫للمباني‬.
.‫وقد‬‫تطور‬‫نظ‬‫ا‬‫الهيكلية‬ ‫م‬‫الشبكية‬‫لألبنية‬‫طويل‬‫ة‬‫القامة‬‫الشاهق‬ ‫االرتفاع‬ ‫وذات‬
‫السحاب‬ ‫ناطحات‬ ‫في‬ ‫كما‬‫أس‬ ‫على‬‫الجديدة‬ ‫الهيكلية‬ ‫المفاهيم‬ ‫اس‬‫للشبكيات‬
‫مع‬‫امتالك‬‫البناء‬ ‫وأساليب‬ ‫حديثا‬ ‫المعتمدة‬ ‫القوة‬ ‫عالية‬ ‫مواد‬‫من‬"‫صالبة‬"‫و‬"‫خفة‬‫الوزن‬
".‫الهيكلية‬ ‫النظم‬ ‫وأصبحت‬"‫أخف‬"‫وتركيبا‬ ‫وزنا‬‫و‬"‫صالبة‬".
‫و‬ ‫مباشرة‬ ‫من‬ ‫بدال‬ ‫أنه‬ ‫المعروف‬ ‫ومن‬‫قف‬‫القوى‬ ‫تأثي‬‫منها‬ ‫الحد‬ ‫األفضل‬ ‫فمن‬‫وتبديد‬‫وتقليل‬
‫االهتزازات‬ ‫حجم‬.
-‫ويخضع‬‫تأثير‬ ‫الى‬ ‫العالية‬ ‫المباني‬ ‫هيكل‬ ‫تصميم‬‫والزالزل‬ ‫الرياح‬ ‫عن‬ ‫الناجمة‬ ‫الجانبية‬ ‫األحمال‬.
‫حيث‬‫توفير‬ ‫يتم‬‫و‬‫األ‬ ‫مقاومة‬‫حم‬‫ا‬‫ل‬‫جملة‬ ‫قبل‬ ‫من‬ ‫للهيكل‬ ‫الجانبية‬ ‫والقوى‬
‫نظام‬‫هيكلي‬ ‫انشائي‬‫داخلي‬‫ثنائية‬ ‫مختلطة‬ ‫جمل‬ ‫الى‬ ‫للعزوم‬ ‫مقاومة‬ ‫اطارات‬ ‫من‬
‫االطارات‬ ‫من‬‫القصيى‬ ‫والجدران‬
-‫أو‬‫وفق‬‫الخارجي‬ ‫الهيكلي‬ ‫النظام‬‫الشبكية‬ ‫االطارات‬ ‫وجملة‬Diagrid‫لألحمال‬ ‫المقاومة‬
‫الري‬ ‫من‬ ‫والجانبية‬ ‫الثقالة‬‫اح‬‫والزالزل‬ ‫ح‬
‫ي‬‫الهيكلي‬ ‫النظام‬ ‫يكون‬ ‫أن‬ ‫جب‬‫ا‬‫ل‬‫مختار‬‫فعال‬ ‫بشكل‬ ‫تستخدم‬ ‫أن‬ ‫ينبغي‬ ‫الذي‬ ‫النوع‬ ‫من‬
‫الهيكلية‬ ‫االحتياجات‬ ‫لتلبية‬‫و‬‫ا‬‫ل‬‫م‬‫ع‬‫م‬‫ا‬‫ر‬‫ي‬‫ة‬‫ف‬‫ي‬‫ا‬‫أل‬‫ب‬‫ن‬‫ي‬‫ة‬‫ا‬‫ل‬‫ع‬‫ا‬‫ل‬‫ي‬‫ة‬
‫مؤخرا‬‫و‬‫ح‬‫د‬‫ي‬‫ث‬‫ا‬‫النظا‬ ‫اعتماد‬ ‫تم‬‫الهيكلي‬ ‫م‬diagrid‫في‬‫ا‬‫أل‬‫ب‬‫ن‬‫ي‬‫ة‬‫الكفاءة‬ ‫بسبب‬ ‫الشاهقة‬
‫ا‬‫ل‬‫ع‬‫ا‬‫ل‬‫ي‬‫ة‬‫م‬‫ن‬‫الهيكلية‬‫ا‬‫ل‬‫ى‬‫ج‬‫ا‬‫ن‬‫ب‬‫المرونة‬‫و‬‫م‬‫و‬‫ا‬‫ك‬‫ب‬‫ة‬‫ا‬‫ل‬‫ت‬‫ط‬‫و‬‫ر‬‫المعماري‬ ‫التخطيط‬ ‫في‬.
-‫ه‬‫ذ‬‫ه‬‫ا‬‫ل‬‫ش‬‫ب‬‫ك‬‫ي‬‫ا‬‫ت‬‫ا‬‫ل‬‫ف‬‫ر‬‫ا‬‫غ‬‫ي‬‫ة‬‫و‬‫ا‬‫ل‬‫س‬‫ط‬‫و‬‫ح‬‫ا‬‫ل‬‫م‬‫ت‬‫م‬‫و‬‫ج‬‫ة‬‫و‬‫ا‬‫ل‬‫م‬‫ن‬‫ح‬‫ي‬‫ة‬‫و‬‫ا‬‫ال‬‫ض‬‫ال‬‫ع‬‫ا‬‫ل‬‫م‬‫ا‬‫ئ‬‫ل‬‫ة‬‫ب‬‫أ‬‫ش‬‫ك‬‫ا‬‫ل‬‫ه‬‫ا‬‫ا‬‫ل‬‫ه‬‫ن‬‫د‬‫س‬‫ي‬‫ة‬
‫ف‬‫ي‬‫و‬‫ا‬‫ج‬‫ه‬‫ا‬‫ت‬‫ا‬‫ل‬‫م‬‫ب‬‫ا‬‫ن‬‫ي‬‫ا‬‫ل‬‫ع‬‫ا‬‫ل‬‫ي‬‫ة‬‫ل‬‫ي‬‫س‬‫ت‬‫ه‬‫ي‬‫ف‬‫ق‬‫ط‬‫ت‬‫ر‬‫ف‬‫و‬‫ل‬‫و‬‫ح‬‫ا‬‫ت‬‫م‬‫ع‬‫م‬‫ا‬‫ر‬‫ي‬‫ة‬‫ت‬‫ز‬‫ي‬‫ن‬‫ي‬‫ة‬‫و‬‫ل‬‫ي‬‫س‬‫ت‬‫ه‬‫د‬‫ر‬‫ل‬‫ل‬‫د‬‫و‬‫ال‬‫ر‬‫ا‬‫ت‬
‫ا‬‫و‬‫ن‬‫ز‬‫و‬‫ة‬‫م‬‫ع‬‫م‬‫ا‬‫ر‬‫ي‬‫ة‬
‫ب‬‫ل‬‫ه‬‫ي‬‫م‬‫ن‬‫ص‬‫ل‬‫ب‬‫ا‬‫ل‬‫ج‬‫م‬‫ل‬‫ة‬‫ا‬‫ال‬‫ن‬‫ش‬‫ا‬‫ئ‬‫ي‬‫ة‬‫ا‬‫ل‬‫ذ‬‫ي‬‫ي‬‫ح‬‫ت‬‫ا‬‫ج‬‫ه‬‫ا‬‫ا‬‫ل‬‫م‬‫ه‬‫ن‬‫د‬‫س‬‫ا‬‫ال‬‫ن‬‫ش‬‫ا‬‫ئ‬‫ي‬‫ل‬‫ث‬‫ب‬‫ا‬‫ت‬‫و‬‫ت‬‫و‬‫ا‬‫ز‬‫ن‬
‫ا‬‫ل‬‫م‬‫ن‬‫ش‬‫أ‬‫ك‬‫م‬‫ا‬‫ن‬‫ح‬‫ت‬‫ا‬‫ج‬‫ا‬‫ل‬‫ك‬‫و‬‫ر‬‫و‬‫ا‬‫ل‬‫ج‬‫د‬‫ر‬‫ا‬‫ن‬‫ا‬‫ل‬‫ق‬‫ص‬‫ي‬‫ى‬‫ة‬‫و‬‫ا‬‫ال‬‫ط‬‫ا‬‫ر‬‫ا‬‫ت‬‫ف‬‫ي‬‫ا‬‫ل‬‫د‬‫ا‬‫خ‬‫ا‬‫ل‬
-‫ن‬‫ح‬‫ت‬‫ا‬‫ج‬‫ه‬‫ذ‬‫ه‬‫ا‬‫ل‬‫ش‬‫ب‬‫ك‬‫ي‬‫ا‬‫ت‬‫و‬‫ا‬‫ال‬‫ط‬‫ا‬‫ر‬‫ا‬‫ت‬‫ا‬‫ل‬‫م‬‫ا‬‫ئ‬‫ل‬‫ة‬‫و‬‫ا‬‫ل‬‫م‬‫ت‬‫م‬‫و‬‫ج‬‫ة‬‫ف‬‫ي‬‫ا‬‫ل‬‫خ‬‫ا‬‫ر‬‫ج‬‫ك‬‫ج‬‫م‬‫ل‬‫ا‬‫ن‬‫ش‬‫ا‬‫ئ‬‫ي‬‫ة‬‫م‬‫ق‬‫ا‬‫و‬‫م‬‫ة‬
‫ل‬‫ل‬‫ر‬‫ي‬‫ا‬‫ح‬‫و‬‫ا‬‫ل‬‫ز‬‫ال‬‫ز‬‫ل‬‫ك‬‫و‬‫ا‬‫ج‬‫ه‬‫ا‬‫ت‬‫م‬‫ع‬‫م‬‫ا‬‫ر‬‫ي‬‫ة‬‫ا‬‫ن‬‫ش‬‫ا‬‫ئ‬‫ي‬‫ة‬
‫و‬‫ت‬‫غ‬‫ن‬‫ي‬‫ع‬‫ن‬‫ا‬‫س‬‫ت‬‫ع‬‫م‬‫ا‬‫ل‬‫ن‬‫ظ‬‫ا‬‫م‬‫ا‬‫ل‬‫ق‬‫د‬‫ي‬‫م‬‫ا‬‫ل‬‫ت‬‫ص‬‫ا‬‫ل‬‫ب‬‫ا‬‫ل‬‫ق‬‫ط‬‫ر‬‫ي‬bracing‫ل‬‫أل‬‫ع‬‫م‬‫د‬‫ة‬‫ا‬‫ل‬‫خ‬‫ا‬‫ر‬‫ج‬‫ي‬‫ة‬
‫و‬‫ا‬‫ل‬‫ذ‬‫ي‬‫ا‬‫ح‬‫ي‬‫ا‬‫ن‬‫ا‬‫ال‬‫ي‬‫ر‬‫ض‬‫ي‬‫ا‬‫ل‬‫م‬‫ا‬‫ل‬‫ك‬‫و‬‫ال‬‫ي‬‫و‬‫ح‬‫ي‬‫ب‬‫أ‬‫د‬‫ن‬‫ى‬‫ج‬‫م‬‫ا‬‫ل‬‫م‬‫ع‬‫م‬‫ا‬‫ر‬‫ي‬

10. 10

11. 11
Diagrid Structural System
Def In general, structural systems are groups of interacting components that function
as one, to safely transmit gravitational and lateral loads to the ground. A Diagrid is a form of
such system. However, compared to conventional framing systems, Diagrids transfer loads
more efficiently as it combine gravitational and lateral resisting systems into one, through the
use of repetitive triangular framing. Such framing is used because of the efficient shape of a
triangle, which does not deform easily as each member is braced by the other two.
cause of this feature, Diagrids can span greater lengths and do not require interior columns, thus
increasing useable space in a building. In addition, the ability of a Diagrid system to dissipate
loads quicker with lesser building materials, allow design of more complex yet lighter structures,
making it an efficient system to use in sky scrapers and high rise buildings.

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Typical Diagrid Connection
 Nodes
o Joints that connects all the members
o Typically formed by bolting or welding the ends of the members to a gusset plate
 Diagonal Members
o Members that transfer both lateral and gravity loads through axial action
 Horizontal Members
o Members that transfer gravitational loads to diagonal members through shear
action Members that transfer lateral loads to diagonal members through axial action
Load Distribution
The load distribution in a Diagid is similar to that of a truss, where loads applied at the
nodes are transferred by each each member through axial forces. However, unlike trusses
where one basic assumption is that all loads are applied at nodes (thus eliminating shear
forces), analysis of Diagrid systems include non-nodal loads, which induce shear forces.
The following figure shows the load path in a Diagrid system under a gravity point
load. As evident from the figure, the nodal load is transmitted by the diagonal members,
quickly dissipating the load.

13. 13
Load Path in a Diagrid Under a Gravity Point Load
Similar to this load distribution is that of a lateral point load applied at a node. The
diagonal members serves as a brace frame, which transmits the lateral loads axially to the
ground. The following figure shows this load path.
Load Path in a Diagrid Where

14. 14
Lateral Loads are Applied at the Nodes
However, for the transmission of distributed loads or loads that are not applied at the
nodes, horizontal members transfer loads to diagonal members through shear forces. The
following figure shows how the loads are transmitted to the ground. The green lines show
the transfer of loads by shear action, while the red lines show transfer through axial action.
Load Path in a Diagrid System Under

15. 15
Distributed Gravity Loads
The load paths shown verifies the ability of a Diagrid system to provide both lateral
and gravity support in one system. The diagonals, as stated earlier, provides a quicker way
of transferring loads to the ground through axial forces, while horizontal may transfer forces
axially or by shear, depending on the type of loading applied.
Compared to conventional framing, Diagrid systems have a wider spread of loads,
and lesser contact with ground (as it has lesser members), which may affect the selection of
its foundation system. Depending on the foundation system chosen, Diagrids may require
lesser support. For instance, for a deep foundation, Diagrids may require less piles, since
there is less members and concentrated loads.

16. 16

17. 17

18. 18

19. 19
Cybertecture Egg, Mumbai, India Capital Gate, Abu Dhabi, United Arab Emirates Al Faisaliah Tower 2, R
iyadh ,
Saudia Arabia
How diagrid system adopt in high-rise building?
Background of "diagrid" structure
The early era, tall building relied on portal frame and fix joint to resist lateral and wind
load. Latter the structure build higher, more load and forces have to consider in the
structure. Additional bracing in the form of diagonal placed in between the structure to
take the lateral load. Portal frames are insufficient in the lateral forces for the tall
building. Diagonal bracing make the structure resist wind forces instead creating
stronger frame connection

20. 20
How diagrid works?
Original diagonal bracing member laid over exterior structure as supplementary support.
However, the current diagrid system that used in exterior structures is primary mean of
support. Diagrid tower is model as vertical cantilever. The size of diagonal grid is defined
by the diving tower height into series of modules.
Diagrid “tube” does not have the sufficient strength to achieve stability in the structure.
Ring beam connection to the floor edge can tied diagrid with the floor and the core.
Normally multiple floors interesting with each long diagonal of the grid, these intersections

21. 21
will occur at the nodes as well as the several instances along the diagonal. When the
diagonal bracing extends over several stories, each floor’s edge beam can frame into the
diagonal members providing connection the core to support the floor edge beam.
“diagrid is a series of triangle that combine gravity and
lateral support into one, making the building to be stiff,
efficient, and lighter than a traditional high rise”
These diagonals were affected by the width and height ratio.
The base of the building have to designed to resist moment while the top have to resist the
shear force. As a result, the foundation of a diagrid system is more concentrate on a point
to reach stability yet the bundle tube system are relying of greater surface area.
What make Diagrid Structure works ?
- Diagrid structure required overall building plan dimension to counteracting the overturning
moment and provide rigidity though axial action in the diagonal members rather bending
moment in beams and column.
- Diagrid system maximum shear rigidity once the module reach equal 35° . However, the
maximum engagement of the diagonal member for bending stiffness corresponds to value
90 °. Vertical columns can be eliminated but the diagrid system relies on the optical angle
and module dimension.
- The diagonal members in diagrid carry shear and moment. The optical angle of the
diagrid will dependent on the building height and module. The expected optimal angle for
diagonal members for diagrid structure will fall in the rage of 60° to 70°.
Who mentioned that, “ a pure steel diagrid tower doesnot require a core for lateral
resistance
Diagrid nodes
The relatively new and the joints off diagrid are more complicated than conventional frame
structure.
The fabrication of the connection and joint are much complex than conventional rectilinear
structure. So shop fabrication before send to site work is needed.

22. 22
There are two school interpreting the need of node
(1) pin node
Not rigid pin connection can be used in the symmetrical structure since the structure have
balance load.
(2) Rigid Node
the needs of rigid nodes to assist the structure to support during the construction process.
Diagrams show the function responding to the load: Under vertical load (left) and under
horizontal load (right)
Diagrid Joint
Welding joint for the Swiss Re Tower interior
There are two type of cladding system which affected by the diagrid type;
(i) diagrid structure sit external and the envelope or curtain wall will clad on floor structure,
(ii) diagrid structure sit internal and the envelope have to clad on the diagrid.
This tend to change the typical rectilinear curtain wll system into triangulate shapes.
(Boaske, 2013)

23. 23
There are two main joint for the diagrid structure: welding or bolting.
This have to rely on the what appearance require for the design. for example when the
structure to be expose, welding cans provides better aesthetic value. In the contrast,
if the structure will be expose to external and cannot be visible, bolt and nut will be the
better choice.
A welding connection is needed if the diagrid structures decided to architectural exposed it
but required more skillful workers . Somehow, if the structure are to be clad or concealed
like Hearts Tower, the diagrid can choose to bolted on site for speed erection.
Diagrid Load
Vertical - Lateral - Shear through triangulation
Compared with conventional framed tubular structures without diagonals, diagrid structures
are much more effective in minimizing shear deformation because they carry shear by axial
action of the diagonal members, while conventional framed tubular structures carry shear
by the bending of the vertical columns.” (MOON, Connor, & Fernandez, 2007). Below are
the force study diagram from the seminar lesson of EngineerBlog:

24. 24
Vertical Load
The gravity and vertical load from the building will distribute toward the apex of the
diagonal structure. Somehow, it will affected by the height and angle of the diagonal. The
vertical forces will be divide/disperse into the other diagonal member. Compression and
tension result in the diagonal will transfer into the bottom section.
Lateral Load

25. 25
the lateral load happened toward the "flange" of the structure receiving directional wind
load. this will result the lateral load into two part; windward and leeward. As a
consequence, these diagonal members receiving two different direction of force load. It will
respond relatively. The structure able to resist both force and achieve equilibrium.
Shear Load
the shear load happened when the structure receive a moment. This forces react toward
the angle of the apex. Comparing to the conventional frame structure, triangular properties
allow the force to be distribute and achieve a balance. In other hand, it also means that the
more diagonal structure able to transfer the shear load, it cans ensure the structure
standing even though received certain impact that may cause structure failure.

26. 26
‫الشبكية‬ ‫الخاليا‬ ‫جمل‬ ‫انواع‬Diagrid Structural System
-‫المع‬ ‫شبكيات‬ ‫الى‬ ‫باالضافة‬‫والجاهزة‬ ‫الستيل‬ ‫ومقاطع‬ ‫دنية‬‫والبواري‬ ‫االنبوبية‬ ‫البروفيالت‬ ‫من‬
‫الشبكات‬ ‫يوجد‬ ‫كذلك‬‫الصنع‬ ‫مسبقة‬ ‫الى‬ ‫المسلحة‬ ‫الخرسانية‬ ‫والمقاطع‬
-‫الخشبية‬ ‫الشبكيات‬ ‫جملة‬ ‫وكذلك‬
-‫واال‬ ‫األبنية‬ ‫تناسب‬ ‫المعدنية‬ ‫والمقاطع‬ ‫الجمل‬ ‫تبقى‬ ‫لكن‬‫العالية‬ ‫رتفاعات‬‫حتى‬011‫طابق‬
-‫المسلحة‬ ‫البيتنونية‬ ‫والمقاطع‬ ‫الشبكات‬ ‫عكس‬ ‫على‬‫من‬ ‫اكثر‬ ‫ليس‬01‫طابق‬
‫الثقيلة‬ ‫والمقاطع‬ ‫الخرسانية‬ ‫الشدة‬ ‫كلفة‬ ‫زيادة‬ ‫الى‬

27. 27
Diagrid Structural System

28. 28

29. 29

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Figure 5. Aldar HQ in Abu Dhabi is the only circular diagrid tower. The diagrid has been constructed
from standard structural steel(wide flange or universal column sections) and a spray fire protection used.
Capital Gate in Abu Dhabi also uses triangulated glazing but makes a more unobtrusive gesture
on the façade regarding the location of the diagrid situated behind the glass. The very small 2
storey module size for Capital Gate, to support the 18 decree lean, has resulted in one of the
smallest modules to date.
The member sizes are large and to translate this to the façade would have been
quite overbearing. Instead a slight color change at the grid is used to acknowledge the pattern.
These sorts of twisted forms tend to subdue the reading of the module through to the façade.
EXTERIOR DIAGRIDS
The majority of structural diagrids have been placed on the interior of the envelope. This is
especiallycritical in cold climates where thermal expansion is significant and thermal
bridges must be avoided. In highly corrosive environments exterior diagrids can also
require ongoing maintenance due to oxidation and weathering of the finish. However
diagrids have been used outside of the envelope in several instances to satisfy different
programmatic requirements. This is more frequent in hot or temperate climates where
thermal issues are less.
Perhaps the most notable exterior diagrid structure to date is for One Shelley Street in
Sydney, Australia.

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The temperate climate has permitted the diagrid to exist outside of the curtain wall façade,
effectively maximizing the internal leasable area. Although the designers were originally
planning to construct the members from architecturally exposed steel, it was decided for
economic reasons to instead use conventional universal column sections and clad these.
As corrosion resistance is a great concern in Australia, this was likely a prudent decision.
The triangulation of the diagrid is completed by the floor edge beams on the interior.
This is always structurally necessary for stability, but normally this functionality is not
separated by the placement of the curtain wall.
Exterior diagrids are also being used in double façade construction as a lightweight but
stable means to support the outer layer of glazing. Although not structural in terms of the
support of the building, they do take advantage of the structural attributes of diagrid design

35. 35

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the difference between conventional exterior-braced frame structures and current
diagrid structures is that, for diagrid structures, almost all the conventional vertical
columns are eliminated. This is possible because the diagonal members in diagrid
structural systems can carry gravity loads as well as lateral forces owing to their
triangulated configuration, whereas the diagonals in conventional braced frame structures
carry only lateral loads.
Compared with conventional framed tubular structures without diagonals, diagrid
structures are much more effective in minimizing shear deformation because they carry
shear by axial action of the diagonal members,

37. 37
while conventional framed tubular structures carry shear by the bending of the vertical
columns. Diagrid structures do not need high shear rigidity cores because shear can be
carried by the diagrids located on the perimeter Diagrid has good appearance and it is
easily recognized.
The configuration and efficiency of a diagrid system reduce the number of structural
element required on the façade of the buildings, therefore less obstruction to the
outside view. The structural efficiency of diagrid system also helps in avoiding interior
and corner columns, therefore allowing significant flexibility with the floor plan.
Perimeter “diagrid” system saves approximately 20 percent structural steel
weight when compared to a conventional moment-frame structure.
. IBM Building, Pittsburgh DIAGRID STRUCTURAL SYSTEMS

38. 38
Diagrid Structural Systems
Diagrid Structural System‎> ‎Numeric Parameters
Diagrid systems are generally used for high rise towers,
oughly 20 - 100 stories tall, depending on location and
materials used. And the angle of the diagrid is most
effective between 53 and 76 degrees (See figure Below).

39. 39

40. 40
Forces and Deflections/Member Sizing at members at associated floor heights of 60 story building.
Above are the calculated member sizes based on floor height and stresses affected on those
members. Obviously, the higher the member, the lower load associated with that specific member,
and therefore a smaller member is required. Notice that for a 60 story building, the Bending stress
exceeds the shear stress in a member around the 18th story mark, which means that would be the
primary force to pay attention to at the lower levels.

41. 41

42. 42

43. 43

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The diagrid structural system
has been widely used for recent tall buildings due to the structural efficiency and aesthetic
potential provided by the unique geometric configuration of the system. This paper
presents a stiffness-based design methodology for determining preliminary member sizes
of steel diagrid structures for tall buildings.
The methodology is applied to diagrids of various heights and gridgeometries to determine
the optimal grid configuration of the diagrid structure within a certain height range.
Constructability is a serious issue in diagrid structures because the nodes of diagrids are
more complicated than those of conventional orthogonal structures.
Design methodology
A diagrid structure is modeled asa vertical cantilever beam on the ground, and subdivided
longitudinally into modules according to the repetitive diagrid pattern.
Each module is defined by a single level of diagrids that extend over multiple
stories. Figure 2 illustrates the case of a 6-story module. Depending upon the direction of
loading, the faces act as either web planes (i.e., planes parallel to wind) or flange planes
(i.e., planes perpendicular to wind). The diagonal members are assumed to be pin-ended,
and therefore resistthe transverse shear and moment through axial action only.
With this idealization, the design problem reduces to determining the cross-sectional area of
typical web and flange members for each module. Following the design methodology
developed by Moon et al. (2007), member sizes for the modules can be computed using
Equations (1) and (2) customized for each design case.

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Ad,w: Area of Each Diagonal on the Web
Ad,f: Area of Each Diagonal on the Flange
V: Shear Force
M: Moment
Ld: Length of Diagonal
Ed: Modulus of Elasticity of Steel
θ: Angle of Diagonal Member
γ: Transverse Shear Strain
χ: Curvature

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Nd,w: Number of Diagonals on Each Web Plane
Nd,f: Number of Diagonals on Each Flange Plane
δ: Contribution of Web Diagonals for Bending Rigidity
B: Building Width in the Direction of Applied Force
Optimal stiffness-based design corresponds to a state of uniform shear and bending deformation
under the design loading. Uniform deformation states are possible only for statically determinate
structures. Tall building structures can be modeled as verticalcantilever beams on the ground, and
uniform deformation can be achieved for these structures (Connor, 2003). Then, the deflection at
the top, , is given by

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Since, determination of a value for α, which is generally in the neighborhood of 500, is an
engineering decision, it remains to establish a value for ‘s.’ Then, the design of diagonals
in each module can be performed using Equations (1) and (2) customized for each design
case. The following section investigates the impacts of different ‘s’ value selections toward
the optimal stiffness-based design, which uses the least amount of material to meet the
design requirements. Further, diagrids of different height-to-width aspect ratios are
designed with various grid geometries to determine the optimum grid configuration of the
system depending on its aspect ratio.

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CONSTRUCTION OF STEEL DIAGRID STRUCTURES
Node construction for diagrid structures
the joints of diagrid structures
are more complicated and tend to be more expensive than those of conventional
orthogonal structures. In order to reduce jobsite work, prefabrication of nodal
elements is essential. Due to the triangular configuration of the diagrid structural
system, rigid connections are not necessary at the nodes, and pin connections
using bolts can be made more conveniently at the jobsite. Ifconsiderately
designed using appropriate prefabrication strategy, constructability will not be
such a limiting factor of the diagrid structures. Prefabrication of diagrid nodes for
conventional rectangular shape buildings can be done relatively easily and
economically because many nodes ofthe same configuration are required in this
case.

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Node detail for a freeform diagrid building

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Façade construction for diagrid structures
Different from conventional orthogonal structures, which are generally clad with
rectangular shape curtain wall units, diagrid structur esare clad with not only
rectangular but also triangular, diamond or parallelogram shape curtain wall units.
The Hearst Headquarters (Figure 1) uses rectangular shape curtain walls, while
the 30 St.
Mary Axe (Figure 8) uses diamond shape curtain walls.
Figure 9 shows a curtain wall unit of parallelogram shape composed of two
triangles to clad diagrid tall building structure.

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57. 57
:‫والخالصة‬ ‫النتيجة‬
-‫يمكن‬‫الجمل‬ ‫ان‬ ‫القول‬‫القطري‬ ‫الشبكية‬‫ة‬‫وتوازن‬ ‫مقاومة‬ ‫اكثر‬ ‫هي‬
‫العادية‬ ‫االطارات‬ ‫جملة‬ ‫من‬
-‫حيث‬‫الشبكية‬ ‫الجملة‬‫المائلة‬ ‫االضالع‬ ‫ذات‬‫تقاوم‬‫اكثر‬‫من‬‫االنقالب‬ ‫عزم‬
‫الفتل‬ ‫وعزم‬(‫تورشن‬)
‫شكلها‬ ‫خالل‬ ‫من‬‫المتو‬‫الجمال‬ ‫خاصية‬ ‫يزيد‬ ‫والذي‬ ‫والمنحني‬ ‫مج‬
‫المعماري‬‫االنشائي‬ ‫والردع‬
‫لثبات‬ ‫تعمل‬ ‫فهي‬‫البناء‬ ‫وسالمة‬‫االنشائي‬ ‫التوازن‬ ‫وتحقيق‬
‫باالضاف‬‫ة‬‫الى‬‫خاصية‬ ‫تحقيق‬‫الجمال‬‫وال‬‫المعماري‬ ‫ذوق‬

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Dr. Youssef Hammida